There exist many computer programs today that assist a user in editing data on a computer. For example, a word processing program enables a user to enter and modify textual data. A computer-aided drafting program enables a user to enter and modify graphical data. A digital signal-editing program enables a user to load digital signal data, modify the digital signal data, and save the digital signal data. Such a digital signal may represent audio data, for example.
It is common for such a data-editing program to display a visual representation of the data that is being edited. For example, a digital signal-editing program may display a graph on which a time-by-amplitude representation of an audio signal is plotted. In response to a user's command to perform a particular operation relative to the data, the visual representation typically changes instantaneously from a pre-operation image of the data to a completely post-operation image of the data. Thus, each operation may be seen to correspond to exactly two different “frames” of reference: a “before” frame in which the data appears without any of the effects of the operation, and an “after” frame in which the data appears with all of the effects of the operation.
The editing operations that are performed relative to data might have very subtle effects on the data. Sometimes, an operation's effect on data may be so subtle that a visual representation of the data before the operation may appear to be very similar to a visual representation of the data after the operation. In such circumstances, it can be very difficult for a user to determine, based on the visual representation, whether the data changed at all, and in what manner.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.